1. Field of the Invention
The invention relates to a stator of a rotary electric machine, and more particularly, to a stator of a rotary electric machine in which a winding is formed using a conductor segment coil.
2. Description of Related Art
To form a coil that is wound around a stator of a rotary electric machine, a U-shaped conductor segment is inserted into a slot from one side in an axial direction of a stator core, and a tip end portion that protrudes on the other side in the axial direction is bent and sequentially connected.
For example, Japanese Patent Application Publication No. 2011-135733 (JP 2011-135733 A) describes a coil of a stator core of a rotary electric machine in which a conductor of a single sectional area is wound according to related art, wherein a sectional area of a slot portion is made smaller than the single sectional area, and a sectional area of a coil end portion is made larger than the single sectional area.
Also, Japanese Patent Application Publication No. 2003-259584 (JP 2003-259584 A) describes technology in which a slot portion of a conductor segment used in a stator of an alternating current generator for a vehicle is deformed by rolling or the like so as to have a generally rectangular shaped cross-section, and a turn portion of the conductor segment has a cross-section that remains the cross-section of round wire.
Japanese Patent Application Publication No. 2003-32933 (JP 2003-32933 A) describes technology related to a conductor segment used in a stator of an alternating current generator for a vehicle, in which, when a sectional area of a coil end portion is designated A1, a sectional area of a slot portion is designated A2, and a sectional area of an end portion is designated A3, in a first example embodiment A2 and A3 remain having rectangular cross-sections and A1 is press-formed so as to have a circular cross-section, and in a second example embodiment A1 and A2 remain having rectangular cross-sections and A3 is press-formed so as to have a circular cross-section, and in a third example embodiment A2 remains having a rectangular cross-section and A1 and A3 are press-formed so as to have circular cross-sections, and in a fourth example embodiment A2 remains having a circular cross-section and A1 and A3 are press-formed so as to have rectangular cross-sections.
When the conductor sectional area of the coil is decreased, the space factor of the conductor in the slot of the stator core improves, but resistance becomes greater and copper loss increases. If the conductor sectional area of the coil end portion is increased as it is in JP 2011-135733 A, JP 2003-259584 A, and JP 2003-32933 A, copper loss at that portion is able to be reduced. However, when a conductor segment coil is used, the U-shaped portion and the portion on a tip end of a leg portion become the coil end, and if the sectional area of the portion at the tip end is increased, insertability into the slot decreases (i.e., it is more difficult to insert the conductor segment coil into the slot).